Phase interpolators are devices which receive two or more input signals which typically have a same frequency, but different phases. The phase interpolator then generates at least one further signal which typically also has the same frequency and a phase which is between the phases of the at least two input signals. Via a control signal, the phase of the signal output by the phase interpolator may be adjustable. Such phase interpolators conventionally are for example employed in phase-locked loops (PLLs) and/or clock and data recovery circuits (CDR), but may also be used in other applications where a signal with a desired phase is to be generated.
One kind of phase interpolators is for example a current steering phase interpolator, where a current from one or more current sources is selectively routed to input devices receiving input signals having different phases. A phase of an output signal then depends on a distribution of the current to the input devices. These and other phase interpolators may suffer from nonlinearities, for example an integral nonlinearity (INL) which may describe a deviation of the phase of the output signal depending on a control signal, for example a digital control word, from an ideal linear behaviour. Such an integral nonlinearity may for example include an intrinsic integrated nonlinearity of the phase interpolator, for example due to interpolation of signals having a sinusoidal waveform. A weighted addition of such signals may generally exhibit a nonlinear behaviour. The integrated nonlinearity may also comprise nonlinearities caused for example by a mismatch of devices of or components of the phase interpolator (for example mismatch of transistors) or nonlinearities caused by a distortion of input waveforms like the above-mentioned sinusoidal waveforms. However, for some applications, an improved linearity would be desirable.